Cell Division II | Biology

<!DOCTYPE html> <html lang="en" dir="ltr"> <head>  <meta http-equiv="X-UA-Compatible" content="ie=edge"> <meta charset="utf-8"> <base href="https://www.visionlearning.com"> <title>Cell Division II | Biology | Visionlearning</title> <link rel="canonical" href="https://www.visionlearning.com/en/library/biology/2/cell-division-ii/212"> <meta name="description" content="Beginning with the discovery of mitosis, the module details each phase of this cell process. It provides an overview of the structure of cell components that are critical to mitosis. The module describes Clark Noble’s experiments with the Madagascar Periwinkle, which led to the discovery of an effective cancer treatment drug. The relationship between mitosis and cancer is explored as is the mechanism by which anti-cancer drugs work to slow down or prevent cell division."> <meta name="keywords" content="cell division, mitosis, genetic material, DNA, nucleus"> <meta name="viewport" content="width=device-width, initial-scale=1.0, shrink-to-fit=no"> <meta name="msvalidate.01" content="D8E20F39AD48052260032E56DE409970"> <script type="application/ld+json"> { "@context": "http://schema.org/", "@type": "Article", "mainEntityOfPage": { "@type": "WebPage", "@id": "https://visionlearning.com/en/library/biology/2/cell-division-ii/212" }, "name": "Cell Division II", "headline": "Cell Division II: Mitosis", "author": [ { "@type": "Person", "name": "David Warmflash, MD" } , { "@type": "Person", "name": "Nathan H Lents, Ph.D." }], "datePublished": "2015-06-21 18:09:21", "dateModified": "2017-02-12T08:30:00+05:00", "image": { "@type": "ImageObject", "url": "/img/library/moduleImages/featured_image_212-23061209062750.jpg", "width": 696, "height": 464 }, "publisher": { "@type": "Organization", "name": "Visionlearning, Inc.", "logo": { "@type": "ImageObject", "url": "http://visionlearning.com/images/logo.png", "width": 278, "height": 60 } }, "description": "Beginning with the discovery of mitosis, the module details each phase of this cell process. It provides an overview of the structure of cell components that are critical to mitosis. The module describes Clark Noble’s experiments with the Madagascar Periwinkle, which led to the discovery of an effective cancer treatment drug. The relationship between mitosis and cancer is explored as is the mechanism by which anti-cancer drugs work to slow down or prevent cell division.", "keywords": "cell division, mitosis, genetic material, DNA, nucleus", "inLanguage": { "@type": "Language", "name": "English", "alternateName": "en" }, "copyrightHolder": { "@type": "Organization", "name": "Visionlearning, Inc." }, "copyrightYear": "2015"} </script> <meta property="og:url" content="https://visionlearning.com/en/library/biology/2/cell-division-ii/212"> <meta property="og:title" content="Cell Division II | Biology | Visionlearning" /> <meta property="og:type" content="website"> <meta property="og:site_name" content="Visionlearning"> <meta property="og:description" content="Beginning with the discovery of mitosis, the module details each phase of this cell process. It provides an overview of the structure of cell components that are critical to mitosis. The module describes Clark Noble’s experiments with the Madagascar Periwinkle, which led to the discovery of an effective cancer treatment drug. 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Services</a></li> <li><a href="/en/library/environmental-science/61/population-biology/287">Population Biology</a></li> </ul> </div> <button class="accordion__button" id="acc-button-earth-cycles" data-accordion="button" aria-controls="acc-panel-earth-cycles" aria-expanded="false"> <span class="accordion__button__label"> Earth Cycles </span> </button> <div class="accordion__panel" id="acc-panel-earth-cycles" data-accordion="panel" aria-labelledby="acc-button-earth-cycles" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/environmental-science/61/the-nitrogen-cycle/98">The Nitrogen Cycle</a></li> <li><a href="/en/library/environmental-science/61/the-carbon-cycle/95">The Carbon Cycle</a></li> <li><a href="/en/library/environmental-science/61/the-phosphorus-cycle/197">The Phosphorus Cycle</a></li> </ul> </div> <button class="accordion__button" id="acc-button-scientific-research" data-accordion="button" aria-controls="acc-panel-scientific-research" aria-expanded="false"> <span class="accordion__button__label"> Scientific Research </span> </button> <div class="accordion__panel" id="acc-panel-scientific-research" data-accordion="panel" aria-labelledby="acc-button-scientific-research" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/environmental-science/61/collaborative-research-in-the-arctic-towards-understanding-climate-change/183">Collaborative Research in the Arctic Towards Understanding Climate Change</a></li> <li><a href="/en/library/environmental-science/61/atmospheric-chemistry-research-that-changed-global-policy/211">Atmospheric Chemistry Research that Changed Global Policy</a></li> </ul> </div> </div> </div> <button class="accordion__button" id="acc-button-general-science" data-accordion="button" aria-controls="acc-panel-general-science" aria-expanded="false"> <span class="accordion__button__label"> General Science </span> </button> <div class="accordion__panel" id="acc-panel-general-science" data-accordion="panel" aria-labelledby="acc-button-general-science" role="region"> <div class="accordion accordion--secondary"> <button class="accordion__button" id="acc-button-methods" data-accordion="button" aria-controls="acc-panel-methods" aria-expanded="false"> <span class="accordion__button__label"> Methods </span> </button> <div class="accordion__panel" id="acc-panel-methods" data-accordion="panel" aria-labelledby="acc-button-methods" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/general-science/3/the-scientific-method/45">The Scientific Method</a></li> </ul> </div> <button class="accordion__button" id="acc-button-measurement" data-accordion="button" aria-controls="acc-panel-measurement" aria-expanded="false"> <span class="accordion__button__label"> Measurement </span> </button> <div class="accordion__panel" id="acc-panel-measurement" data-accordion="panel" aria-labelledby="acc-button-measurement" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/general-science/3/the-metric-system/47">The Metric System</a></li> </ul> </div> <button class="accordion__button" id="acc-button-physical-properties" data-accordion="button" aria-controls="acc-panel-physical-properties" aria-expanded="false"> <span class="accordion__button__label"> Physical Properties </span> </button> <div class="accordion__panel" id="acc-panel-physical-properties" data-accordion="panel" aria-labelledby="acc-button-physical-properties" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/general-science/3/temperature/48">Temperature</a></li> <li><a href="/en/library/general-science/3/density-and-buoyancy/37">Density and Buoyancy</a></li> </ul> </div> </div> </div> <button class="accordion__button" id="acc-button-math-in-science" data-accordion="button" aria-controls="acc-panel-math-in-science" aria-expanded="false"> <span class="accordion__button__label"> Math in Science </span> </button> <div class="accordion__panel" id="acc-panel-math-in-science" data-accordion="panel" aria-labelledby="acc-button-math-in-science" role="region"> <div class="accordion accordion--secondary"> <button class="accordion__button" id="acc-button-equations" data-accordion="button" aria-controls="acc-panel-equations" aria-expanded="false"> <span class="accordion__button__label"> Equations </span> </button> <div class="accordion__panel" id="acc-panel-equations" data-accordion="panel" aria-labelledby="acc-button-equations" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/math-in-science/62/unit-conversion/144">Unit Conversion</a></li> <li><a href="/en/library/math-in-science/62/linear-equations/194">Linear Equations</a></li> <li><a href="/en/library/math-in-science/62/exponential-equations-i/206">Exponential Equations I</a></li> <li><a href="/en/library/math-in-science/62/exponential-equations-ii/210">Exponential Equations II</a></li> <li><a href="/en/library/math-in-science/62/scientific-notation/250">Scientific Notation</a></li> <li><a href="/en/library/math-in-science/62/measurement/257">Measurement</a></li> </ul> </div> <button class="accordion__button" id="acc-button-statistics" data-accordion="button" aria-controls="acc-panel-statistics" aria-expanded="false"> <span class="accordion__button__label"> Statistics </span> </button> <div class="accordion__panel" id="acc-panel-statistics" data-accordion="panel" aria-labelledby="acc-button-statistics" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/math-in-science/62/introduction-to-descriptive-statistics/218">Introduction to Descriptive Statistics</a></li> <li><a href="/en/library/math-in-science/62/introduction-to-inferential-statistics/224">Introduction to Inferential Statistics</a></li> <li><a href="/en/library/math-in-science/62/statistical-techniques/239">Statistical Techniques</a></li> </ul> </div> <button class="accordion__button" id="acc-button-trigonometric-functions" data-accordion="button" aria-controls="acc-panel-trigonometric-functions" aria-expanded="false"> <span class="accordion__button__label"> Trigonometric Functions </span> </button> <div class="accordion__panel" id="acc-panel-trigonometric-functions" data-accordion="panel" aria-labelledby="acc-button-trigonometric-functions" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/math-in-science/62/wave-mathematics/131">Wave Mathematics</a></li> </ul> </div> </div> </div> <button class="accordion__button" id="acc-button-physics" data-accordion="button" aria-controls="acc-panel-physics" aria-expanded="false"> <span class="accordion__button__label"> Physics </span> </button> <div class="accordion__panel" id="acc-panel-physics" data-accordion="panel" aria-labelledby="acc-button-physics" role="region"> <div class="accordion accordion--secondary"> <button class="accordion__button" id="acc-button-light-and-optics" data-accordion="button" aria-controls="acc-panel-light-and-optics" aria-expanded="false"> <span class="accordion__button__label"> Light and Optics </span> </button> <div class="accordion__panel" id="acc-panel-light-and-optics" data-accordion="panel" aria-labelledby="acc-button-light-and-optics" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/physics/24/the-nature-of-light/132">The Nature of Light</a></li> <li><a href="/en/library/physics/24/electromagnetism-and-light/138">Electromagnetism and Light</a></li> </ul> </div> <button class="accordion__button" id="acc-button-mechanics" data-accordion="button" aria-controls="acc-panel-mechanics" aria-expanded="false"> <span class="accordion__button__label"> Mechanics </span> </button> <div class="accordion__panel" id="acc-panel-mechanics" data-accordion="panel" aria-labelledby="acc-button-mechanics" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/physics/24/defining-energy/199">Defining Energy</a></li> <li><a href="/en/library/physics/24/waves-and-wave-motion/102">Waves and Wave Motion</a></li> <li><a href="/en/library/physics/24/gravity/118">Gravity</a></li> <li><a href="/en/library/physics/24/thermodynamics-i/200">Thermodynamics I</a></li> </ul> </div> </div> </div> <button class="accordion__button" id="acc-button-process-of-science" data-accordion="button" aria-controls="acc-panel-process-of-science" aria-expanded="false"> <span class="accordion__button__label"> Process of Science </span> </button> <div class="accordion__panel" id="acc-panel-process-of-science" data-accordion="panel" aria-labelledby="acc-button-process-of-science" role="region"> <div class="accordion accordion--secondary"> <button class="accordion__button" id="acc-button-introduction" data-accordion="button" aria-controls="acc-panel-introduction" aria-expanded="false"> <span class="accordion__button__label"> Introduction </span> </button> <div class="accordion__panel" id="acc-panel-introduction" data-accordion="panel" aria-labelledby="acc-button-introduction" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/process-of-science/49/the-process-of-science/176">The Process of Science</a></li> </ul> </div> <button class="accordion__button" id="acc-button-the-culture-of-science" data-accordion="button" aria-controls="acc-panel-the-culture-of-science" aria-expanded="false"> <span class="accordion__button__label"> The Culture of Science </span> </button> <div class="accordion__panel" id="acc-panel-the-culture-of-science" data-accordion="panel" aria-labelledby="acc-button-the-culture-of-science" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/process-of-science/49/the-nature-of-scientific-knowledge/185">The Nature of Scientific Knowledge</a></li> <li><a href="/en/library/process-of-science/49/scientists-and-the-scientific-community/172">Scientists and the Scientific Community</a></li> <li><a href="/en/library/process-of-science/49/scientific-ethics/161">Scientific Ethics</a></li> <li><a href="/en/library/process-of-science/49/scientific-institutions-and-societies/162">Scientific Institutions and Societies</a></li> </ul> </div> <button class="accordion__button" id="acc-button-ideas-in-science" data-accordion="button" aria-controls="acc-panel-ideas-in-science" aria-expanded="false"> <span class="accordion__button__label"> Ideas in Science </span> </button> <div class="accordion__panel" id="acc-panel-ideas-in-science" data-accordion="panel" aria-labelledby="acc-button-ideas-in-science" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/process-of-science/49/theories-hypotheses-and-laws/177">Theories, Hypotheses, and Laws</a></li> <li><a href="/en/library/process-of-science/49/scientific-controversy/181">Scientific Controversy</a></li> <li><a href="/en/library/process-of-science/49/creativity-in-science/182">Creativity in Science</a></li> </ul> </div> <button class="accordion__button" id="acc-button-research-methods" data-accordion="button" aria-controls="acc-panel-research-methods" aria-expanded="false"> <span class="accordion__button__label"> Research Methods </span> </button> <div class="accordion__panel" id="acc-panel-research-methods" data-accordion="panel" aria-labelledby="acc-button-research-methods" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/process-of-science/49/the-practice-of-science/148">The Practice of Science</a></li> <li><a href="/en/library/process-of-science/49/experimentation-in-scientific-research/150">Experimentation in Scientific Research</a></li> <li><a href="/en/library/process-of-science/49/description-in-scientific-research/151">Description in Scientific Research</a></li> <li><a href="/en/library/process-of-science/49/comparison-in-scientific-research/152">Comparison in Scientific Research</a></li> <li><a href="/en/library/process-of-science/49/modeling-in-scientific-research/153">Modeling in Scientific Research</a></li> </ul> </div> <button class="accordion__button" id="acc-button-data" data-accordion="button" aria-controls="acc-panel-data" aria-expanded="false"> <span class="accordion__button__label"> Data </span> </button> <div class="accordion__panel" id="acc-panel-data" data-accordion="panel" aria-labelledby="acc-button-data" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/process-of-science/49/data-analysis-and-interpretation/154">Data Analysis and Interpretation</a></li> <li><a href="/en/library/process-of-science/49/uncertainty-error-and-confidence/157">Uncertainty, Error, and Confidence</a></li> <li><a href="/en/library/process-of-science/49/statistics-in-science/155">Statistics in Science</a></li> <li><a href="/en/library/process-of-science/49/using-graphs-and-visual-data-in-science/156">Using Graphs and Visual Data in Science</a></li> </ul> </div> <button class="accordion__button" id="acc-button-scientific-communication" data-accordion="button" aria-controls="acc-panel-scientific-communication" aria-expanded="false"> <span class="accordion__button__label"> Scientific Communication </span> </button> <div class="accordion__panel" id="acc-panel-scientific-communication" data-accordion="panel" aria-labelledby="acc-button-scientific-communication" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/process-of-science/49/understanding-scientific-journals-and-articles/158">Understanding Scientific Journals and Articles</a></li> <li><a href="/en/library/process-of-science/49/utilizing-the-scientific-literature/173">Utilizing the Scientific Literature</a></li> <li><a href="/en/library/process-of-science/49/peer-review-in-scientific-publishing/159">Peer Review in Scientific Publishing</a></li> <li><a href="/en/library/process-of-science/49/the-how-and-why-of-scientific-meetings/186">The How and Why of Scientific Meetings</a></li> </ul> </div> </div> </div> <button class="accordion__button" id="acc-button-scientists-and-research" data-accordion="button" aria-controls="acc-panel-scientists-and-research" aria-expanded="false"> <span class="accordion__button__label"> Scientists and Research </span> </button> <div class="accordion__panel" id="acc-panel-scientists-and-research" data-accordion="panel" aria-labelledby="acc-button-scientists-and-research" role="region"> <div class="accordion accordion--secondary"> <button class="accordion__button" id="acc-button-scientific-research" data-accordion="button" aria-controls="acc-panel-scientific-research" aria-expanded="false"> <span class="accordion__button__label"> Scientific Research </span> </button> <div class="accordion__panel" id="acc-panel-scientific-research" data-accordion="panel" aria-labelledby="acc-button-scientific-research" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/scientists-and-research/58/collaborative-research-in-the-arctic-towards-understanding-climate-change/183">Collaborative Research in the Arctic Towards Understanding Climate Change</a></li> <li><a href="/en/library/scientists-and-research/58/from-stable-chromosomes-to-jumping-genes/184">From Stable Chromosomes to Jumping Genes</a></li> <li><a href="/en/library/scientists-and-research/58/an-elegant-experiment-to-test-the-process-of-dna-replication/187">An Elegant Experiment to Test the Process of DNA Replication</a></li> <li><a href="/en/library/scientists-and-research/58/the-founding-of-neuroscience/233">The Founding of Neuroscience</a></li> <li><a href="/en/library/scientists-and-research/58/tracking-endangered-jaguars-across-the-border/189">Tracking Endangered Jaguars across the Border</a></li> <li><a href="/en/library/scientists-and-research/58/atmospheric-chemistry-research-that-changed-global-policy/211">Atmospheric Chemistry Research that Changed Global Policy</a></li> <li><a href="/en/library/scientists-and-research/58/revolutionizing-medicine-with-monoclonal-antibodies/220">Revolutionizing Medicine with Monoclonal Antibodies</a></li> <li><a href="/en/library/scientists-and-research/58/uncovering-the-mysteries-of-chronic-mountain-sickness/238">Uncovering the Mysteries of Chronic Mountain Sickness</a></li> </ul> </div> <button class="accordion__button" id="acc-button-profiles-in-science" data-accordion="button" aria-controls="acc-panel-profiles-in-science" aria-expanded="false"> <span class="accordion__button__label"> Profiles in Science </span> </button> <div class="accordion__panel" id="acc-panel-profiles-in-science" data-accordion="panel" aria-labelledby="acc-button-profiles-in-science" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/scientists-and-research/58/luis-e.-miramontes/232">Luis E. Miramontes</a></li> <li><a href="/en/library/scientists-and-research/58/bernardo-houssay/237">Bernardo Houssay</a></li> <li><a href="/en/library/scientists-and-research/58/craig-lee/256">Craig Lee</a></li> <li><a href="/en/library/scientists-and-research/58/david-ho/241">David Ho</a></li> <li><a href="/en/library/scientists-and-research/58/louis-tompkins-wright/244">Louis Tompkins Wright</a></li> <li><a href="/en/library/scientists-and-research/58/carlos-j.-finlay/217">Carlos J. Finlay</a></li> <li><a href="/en/library/scientists-and-research/58/cecilia-payne/290">Cecilia Payne</a></li> <li><a href="/en/library/scientists-and-research/58/jazmin-scarlett/291">Jazmin Scarlett</a></li> <li><a href="/en/library/scientists-and-research/58/ramari-stewart/292">Ramari Stewart</a></li> <li><a href="/en/library/scientists-and-research/58/johnson-cerda/300">Johnson Cerda</a></li> <li><a href="/en/library/scientists-and-research/58/ellen-ochoa/201">Ellen Ochoa</a></li> <li><a href="/en/library/scientists-and-research/58/ruth-benerito/205">Ruth Benerito</a></li> <li><a href="/en/library/scientists-and-research/58/franklin-chang-díaz/219">Franklin Chang Díaz</a></li> <li><a href="/en/library/scientists-and-research/58/percy-lavon-julian/221">Percy Lavon Julian</a></li> <li><a href="/en/library/scientists-and-research/58/luis-walter-alvarez/229">Luis Walter Alvarez</a></li> <li><a href="/en/library/scientists-and-research/58/france-anne-dominic-córdova/230">France Anne-Dominic Córdova</a></li> </ul> </div> </div> </div> </div> </div> </li> <li>  <button class="button" data-toggle="dropdown">Biology </button> <div class="nav__dropdown box-shadow-1 padding-1"> <div class="accordion accordion--secondary font-size-sm"> <div class="accordion accordion--secondary"> <button class="accordion__button" id="acc-sub-button-biological-molecules" data-accordion="button" aria-controls="acc-sub-panel-biological-molecules" aria-expanded="false"> <span class="accordion__button__label"> Biological Molecules </span> </button> <div class="accordion__panel" id="acc-sub-panel-biological-molecules" data-accordion="panel" aria-labelledby="acc-sub-button-biological-molecules" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/biology/2/carbohydrates/61">Carbohydrates</a></li> <li><a href="/en/library/biology/2/fats-and-proteins/62">Fats and Proteins</a></li> <li><a href="/en/library/biology/2/biological-proteins/243">Biological Proteins</a></li> <li><a href="/en/library/biology/2/blood-biology-i/242">Blood Biology I</a></li> <li><a href="/en/library/biology/2/lipids/207">Lipids</a></li> </ul> </div> <button class="accordion__button" id="acc-sub-button-cell-biology" data-accordion="button" aria-controls="acc-sub-panel-cell-biology" aria-expanded="false"> <span class="accordion__button__label"> Cell Biology </span> </button> <div class="accordion__panel" id="acc-sub-panel-cell-biology" data-accordion="panel" aria-labelledby="acc-sub-button-cell-biology" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/biology/2/discovery-and-structure-of-cells/64">Discovery and Structure of Cells</a></li> <li><a href="/en/library/biology/2/respiration/285">Respiration</a></li> <li><a href="/en/library/biology/2/membranes-i/198">Membranes I</a></li> <li><a href="/en/library/biology/2/membranes-ii/204">Membranes II</a></li> <li><a href="/en/library/biology/2/cellular-organelles-i/195">Cellular Organelles I</a></li> <li><a href="/en/library/biology/2/cell-division-i/196">Cell Division I</a></li> <li class="current">Cell Division II</li> <li><a href="/en/library/biology/2/membranes-and-chemical-transport/106">Membranes and Chemical Transport</a></li> </ul> </div> <button class="accordion__button" id="acc-sub-button-energy-in-living-systems" data-accordion="button" aria-controls="acc-sub-panel-energy-in-living-systems" aria-expanded="false"> <span class="accordion__button__label"> Energy in Living Systems </span> </button> <div class="accordion__panel" id="acc-sub-panel-energy-in-living-systems" data-accordion="panel" aria-labelledby="acc-sub-button-energy-in-living-systems" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/biology/2/energy-metabolism-i/215">Energy Metabolism I</a></li> <li><a href="/en/library/biology/2/energy-metabolism-ii/225">Energy Metabolism II</a></li> <li><a href="/en/library/biology/2/photosynthesis-i/192">Photosynthesis I</a></li> </ul> </div> <button 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Darwin III</a></li> <li><a href="/en/library/biology/2/adaptation/68">Adaptation</a></li> <li><a href="/en/library/biology/2/taxonomy-i/70">Taxonomy I</a></li> <li><a href="/en/library/biology/2/taxonomy-ii/89">Taxonomy II</a></li> <li><a href="/en/library/biology/2/introduction-to-paleoanthropology/258">Introduction to Paleoanthropology</a></li> <li><a href="/en/library/biology/2/the-piltdown-hoax/263">The Piltdown Hoax</a></li> <li><a href="/en/library/biology/2/future-of-human-evolution/259">Future of Human Evolution</a></li> </ul> </div> <button class="accordion__button" id="acc-sub-button-genetics" data-accordion="button" aria-controls="acc-sub-panel-genetics" aria-expanded="false"> <span class="accordion__button__label"> Genetics </span> </button> <div class="accordion__panel" id="acc-sub-panel-genetics" data-accordion="panel" aria-labelledby="acc-sub-button-genetics" role="region"> <ul class="nav text-color-link"> <li><a 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text-color-link"> <li><a href="/en/library/biology/2/biodiversity-i/276">Biodiversity I</a></li> <li><a href="/en/library/biology/2/ecosystem-services/279">Ecosystem Services</a></li> <li><a href="/en/library/biology/2/animal-ecology/283">Animal Ecology</a></li> <li><a href="/en/library/biology/2/biodiversity-ii/281">Biodiversity II</a></li> <li><a href="/en/library/biology/2/animal-behavior/286">Animal Behavior</a></li> <li><a href="/en/library/biology/2/population-biology/287">Population Biology</a></li> <li><a href="/en/library/biology/2/trophic-ecology/293">Trophic Ecology</a></li> </ul> </div> </div> </div> </div> </li> </ul> </nav>  <div id="theTop"></div> <main id="skip-header-content"> <div class="margin-bottom-5"> <article class="container wide module"> <header class="grid grid--sidebar-right module__header"> <div class="module__header__title"> <span class="subcategory"> <strong><em>Cell Biology</em></strong> </span> <h1>Cell Division II: <sub><em>Mitosis</em></sub></h1> <p class="byline">by David Warmflash, MD, Nathan H Lents, Ph.D.</p> <nav class="module__header__tabs"> <ul class="tabs-nav tabs-nav--horizontal library"> <li> <a href="/en/library/biology/2/cell-division-ii/212/reading" aria-current="page" >Reading</a> </li> <li> <a href="/en/library/biology/2/cell-division-ii/212/quiz">Quiz</a> </li> <li> <a href="/en/library/biology/2/cell-division-ii/212/resources">Teach with this</a> </li> </ul> </nav> </div> <script type="application/ld+json"> { "@context": "http://schema.org", "@type": "AudioObject", "contentUrl": "https://www.visionlearning.com/img/library/moduleAudio/module_212.mp3", "description": "Recording of Cell Division II : Beginning with the discovery of mitosis, the module details each phase of this cell process. It provides an overview of the structure of cell components that are critical to mitosis. The module describes Clark Noble’s experiments with the Madagascar Periwinkle, which led to the discovery of an effective cancer treatment drug. The relationship between mitosis and cancer is explored as is the mechanism by which anti-cancer drugs work to slow down or prevent cell division.", "encodingFormat": "mp3", "name": "module_212.mp3" } </script> <div class="module_header_audio"> <div class="audio-player border border-radius"> <audio id="audio"> <source src="https://www.visionlearning.com/img/library/moduleAudio/module_212.mp3" type="audio/mpeg"> Your browser does not support the audio element. </audio> <div class="audio-player__title"> <p>Listen to this reading</p> <span class="audio-player__timestamp" id="timestamp"> 00:00 </span> </div> <div class="audio-player__controls" id="controls"> <button class="button button--icon-only" id="play-pause-button"> <span class="icon icon-play" aria-hidden="true"></span> </button> <div class="audio-player__progress" id="progress-bar" tabindex="0" aria-valuemin="0" aria-valuemax="100" aria-valuenow="0" aria-label="Use arrow keys to forward or rewind the audio" role="slider"> <div class="audio-player__progress__fill"> <span class="audio-player__thumb"></span> </div> </div> <div class="audio-player__volume-container"> <button id="mute-button"> <span class="icon icon-volume"></span> </button> <div class="audio-player__volume" tabindex="0" aria-valuemin="0" aria-valuemax="100" aria-valuenow="100" aria-label="Use arrow keys to adjust volume" role="slider"> <div class="audio-player__volume__fill"> <span class="audio-player__thumb"></span> </div> </div> </div> </div> </div> </div> </header> <hr class="divider"/>   <div class="grid grid--sidebar-right grid--divider"> <div class="order-2 order-1--lg module__main"> <div class="narrow margin-x-auto margin-y-5"> <div class="accordion margin-bottom-5">  <button class="accordion__button" id="acc-button-key-concepts" data-accordion="button" aria-controls="acc-panel-key-concepts" aria-expanded="true" tabindex="0"> Did you know? </button> <div class="accordion__panel shown show" id="acc-panel-key-concepts" data-accordion="panel" aria-labelledby="acc-button-key-concepts" role="region"> <div class="accordion__panel__content"> <p>Did you know that there is a huge variation in the number of chromosomes in living things? While humans have 46 chromosomes and dogs have 78, one kind of ant has only 2 chromosomes and a type of protozoan has nearly 16,000! But what all these life forms have in common is that their genetic code is copied from cell to cell thanks to the process of mitosis, whereby the nucleus of a cell splits into two before the cell divides.</p> </div> </div>  <button class="accordion__button" id="acc-button-table-of-contents" data-accordion="button" aria-controls="acc-panel-table-of-contents" aria-expanded="false" tabindex="0"> Key concepts </button> <div class="accordion__panel" id="acc-panel-table-of-contents" data-accordion="panel" aria-labelledby="acc-button-table-of-contents" role="region" aria-hidden="true"> <div class="accordion__panel__content"> <ul class="bulleted"> <li><p>The term mitosis refers specifically to the process whereby the nucleus of a eukaryotic cell splits into two identical daughter nuclei prior to cell division.</p></li> <li><p>Mitosis is a cyclical process consisting of five phases that feed into one another: prophase; prometaphase; metaphase; anaphase; telophase.</p></li> <li><p>The rate at which mitosis occurs depends on the cell type. Some cells replicate faster and others slower, and the entire process can be interrupted.</p></li> <li><p>Chromosomes are made of a material called chromatin, which is dispersed throughout the cell nucleus during interphase. During mitosis, however, the chromatin condenses making individual chromosomes visible under an ordinary light microscope.</p></li> </ul> </div> </div>  <button class="accordion__button" id="acc-button-terms-you-should-know" data-accordion="button" aria-controls="acc-panel-terms-you-should-know" aria-expanded="false" tabindex="0"> Terms you should know </button> <div class="accordion__panel" id="acc-panel-terms-you-should-know" data-accordion="panel" aria-labelledby="acc-button-terms-you-should-know" role="region" aria-hidden="true"> <div class="accordion__panel__content"> <dl> <dt><a href="/en/glossary/view/cell">cell </a></dt> <dd> the basic structural unit of all living things </dd> <dt><a href="/en/glossary/view/membrane">membrane </a></dt> <dd> layer of tissue that forms the boundary of a cell or cell part </dd> <dt><a href="/en/glossary/view/nucleus">nucleus </a></dt> <dd> enclosed in a membrane and containing genetic information, the structure within the cells of plants, animals, fungi, and some one-celled organisms</dd> </dl> </div> </div> </div> <hr class="border-color-dark" /> <section> <div class="container narrow"> <p>How do you discover something extraordinarily fundamental that nobody has ever known or seen before? If you have a pretty good idea of what you’re seeking, you might take Walther Flemming’s approach. In <a href="/library/module_viewer.php?mid=196">Cell Division I: The Cell Cycle</a>, we learned that Flemming observed how <mark class="term" data-term="chromosome" data-term-def="The organized genetic structure of DNA with associated proteins that contains the hereditary information necessary for reproduction, protein manufacture, and other functions." data-term-url="/en/glossary/view/chromosome/3760">chromosomes</mark> became visible in patterns that repeated each time the <mark class="term" data-term="cell" data-term-def="The basic structural unit of all living things." data-term-url="/en/glossary/view/cell/8286">cells</mark> of fire salamanders divided. This important discovery was made possible by using various dyes, a technique that Flemming pioneered (Figure 1). This is a good example of how a new instrument or technique can facilitate a discovery, provided that the researcher already knows more or less what he or she <em>might</em> find.</p> <div class="figure"> <figure> <button class="lightbox-button lightbox-button--icon" data-lightbox="" data-lightbox-src="/img/library/large_images/image_6590.jpg"> <img src="/img/library/modules/mid212/Image/VLObject-6590-131031121030.jpg" alt="Figure 1: Flemming's drawing of an insect cell treated with an aniline dye as he saw it under the microscope" /> </button> <figcaption> <p><strong>Figure 1:</strong> Flemming's drawing of an insect cell treated with an aniline dye as he saw it under the microscope</p> <span class="credit">image ©Wikimedia Commons</span> </figcaption> </figure> </div> <p>This was the case with Flemming. Scientists in the preceding years had already been seeing faint structures in <mark class="term" data-term="cell" data-term-def="The basic structural unit of all living things." data-term-url="/en/glossary/view/cell/8286">cells</mark>, but their dyes were not good enough to reveal what any of these structures did. Throughout the 19th century, as microscopes developed, scientists had been seeing clues of structures in dividing cells of <mark class="term" data-term="eukaryote" data-term-def="A single- or multi-cellular organism whose cells contain a distinct nucleus that encloses the organism's genetic material." data-term-url="/en/glossary/view/eukaryote/5297">eukaryotes</mark>. Like Flemming, earlier scientists had been experimenting with dyes. These were not as good as the aniline dyes that would facilitate Flemming’s discovery, but they helped the scientists to see <em>something</em>. Unfortunately, the dyes killed the cells, and since the structures under the microscope were difficult to see as it was, Flemming’s forerunners weren’t sure they were seeing anything characteristic of a live, functional cell. Were they simply artifacts, something that formed only after the cells died? If so, that would not explain how a cell replicates in a living <mark class="term" data-term="organism" data-term-def="Any connected living system, such as an animal, plant, fungus, or bacterium. Organisms may be composed of a single cell or&hellip;" data-term-url="/en/glossary/view/organism/2171">organism</mark>, or <em>in vivo</em>.</p><p>Knowing what he wanted to find, Flemming set out to do a better job of staining the internal details of <mark class="term" data-term="cell" data-term-def="The basic structural unit of all living things." data-term-url="/en/glossary/view/cell/8286">cells</mark>. By doing so, he realized that he could also determine whether the structures were artifacts or part of cellular function. Using the fire salamander embryos, through a long, painstaking process, he cut his samples into very thin slices and treated them with his new dyes. This killed the cells, just as the earlier dyes had killed the cells of other laboratory animals. However, Flemming repeated this technique with many embryos, arresting their life <mark class="term" data-term="process" data-term-def="Method, procedure; series of actions or steps." data-term-url="/en/glossary/view/process/8256">process</mark> at different points in time. This protocol was as much a novel technique as his utilization of the aniline dyes. By stopping the life process at different points, he could investigate whether the structures looked any different at Time A compared with Time B or Time C and so forth.</p><p>It turned out that they <em>did</em> look different, and this proved that the structures were not artifacts. They were part of the life <mark class="term" data-term="process" data-term-def="Method, procedure; series of actions or steps." data-term-url="/en/glossary/view/process/8256">process</mark> of the <mark class="term" data-term="cell" data-term-def="The basic structural unit of all living things." data-term-url="/en/glossary/view/cell/8286">cells</mark>. Coupled with the improving resolution of microscopes of the era, the aniline dyes could make the differing structures clearly visible. This led Flemming to discover the cell process that we call mitosis: division of the <mark class="term" data-term="eukaryotic" data-term-def="Of cells with a nucleus and other organelles that are surrounded by lipid membranes" data-term-url="/en/glossary/view/eukaryotic/6539">eukaryotic</mark> cell <mark class="term" data-term="nucleus" data-term-def="1. [Atomic] A tiny, dense positively charged mass at the heart of an atom. The nucleus is composed of protons and&hellip;" data-term-url="/en/glossary/view/nucleus/1526">nucleus</mark> that occurs just prior to <mark class="term" data-term="cytokinesis" data-term-def="The process of cell division in the eukaryotic cell cycle, characterized by the cytoplasm dividing to form two daughter cells." data-term-url="/en/glossary/view/cytokinesis/10178">cytokinesis</mark>, which is the division of the cell itself. So revealing were the new dyes and so meticulous was his technique that Flemming was able to define the phases of <mark class="term" data-term="mitosis" data-term-def="Process occurring as part of the eukaryotic cell cycle. In mitosis, chromosomes in the cell nucleus separate into two identical chromosome&hellip;" data-term-url="/en/glossary/view/mitosis/10188">mitosis</mark> that we still talk about today (Figure 2).</p> <div class="figure"> <figure> <button class="lightbox-button lightbox-button--icon" data-lightbox="" data-lightbox-src="/img/library/large_images/image_8219.png"> <img src="/img/library/modules/mid212/Image/VLObject-8219-150621030646.png" alt="Figure 2: Flemming's diagram of eukaryotic cell division (1888)." /> </button> <figcaption> <p><strong>Figure 2</strong>: Flemming's diagram of eukaryotic cell division (1888).</p> </figcaption> </figure> </div> <p><section id="toc_1" class=""> <h2>The phases of mitosis</h2></p> <p>Flemming coined the term <em>chromatin</em> to describe the material of which <mark class="term" data-term="chromosome" data-term-def="The organized genetic structure of DNA with associated proteins that contains the hereditary information necessary for reproduction, protein manufacture, and other functions." data-term-url="/en/glossary/view/chromosome/3760">chromosomes</mark> are made. When he observed <mark class="term" data-term="cell" data-term-def="The basic structural unit of all living things." data-term-url="/en/glossary/view/cell/8286">cell</mark> division in the fire salamander embryos, he saw the same pattern of events occur in each cell, beginning with the appearance of visible chromosomes. He described the events as four periods of time, which he named prophase, metaphase, anaphase, and telophase. Today, we speak of five phases, since we split up Flemming’s prophase, the longest phase, into prophase and prometaphase.</p><p>It’s important to remember that the <mark class="term" data-term="process" data-term-def="Method, procedure; series of actions or steps." data-term-url="/en/glossary/view/process/8256">process</mark> of <mark class="term" data-term="cell" data-term-def="The basic structural unit of all living things." data-term-url="/en/glossary/view/cell/8286">cell</mark> division is cyclical, with one phase feeding into the next. For example, telophase overlaps with <mark class="term" data-term="cytokinesis" data-term-def="The process of cell division in the eukaryotic cell cycle, characterized by the cytoplasm dividing to form two daughter cells." data-term-url="/en/glossary/view/cytokinesis/10178">cytokinesis</mark>, the splitting of the rest of the cell that generates the two new <mark class="term" data-term="daughter" data-term-def="A material that is derived from the breakdown or division of another. For example, a product of the radioactive decay of&hellip;" data-term-url="/en/glossary/view/daughter/10177">daughter</mark> cells. Following cytokinesis, the two new cells then go through a long period called interphase, during which each new cell carries out normal life functions and replicates its <mark class="term" data-term="chromatin" data-term-def="Chromatin is the substance inside of the cell's nucleus and it consists of DNA, proteins (primarily histones), and chromosomal RNA. The&hellip;" data-term-url="/en/glossary/view/chromatin/9839">chromatin</mark>, eventually leading to prophase and another cycle of <mark class="term" data-term="mitosis" data-term-def="Process occurring as part of the eukaryotic cell cycle. In mitosis, chromosomes in the cell nucleus separate into two identical chromosome&hellip;" data-term-url="/en/glossary/view/mitosis/10188">mitosis</mark>. Thus, as mitosis begins, the <mark class="term" data-term="nucleus" data-term-def="1. [Atomic] A tiny, dense positively charged mass at the heart of an atom. The nucleus is composed of protons and&hellip;" data-term-url="/en/glossary/view/nucleus/1526">nucleus</mark> already contains a double set of chromatin. Since chromatin contains the <mark class="term" data-term="gene" data-term-def="Material (usually DNA) that is inherited from a parent and which encodes for a cellular component important for some cellular function." data-term-url="/en/glossary/view/gene/3294">genes</mark> that give <mark class="term" data-term="organism" data-term-def="Any connected living system, such as an animal, plant, fungus, or bacterium. Organisms may be composed of a single cell or&hellip;" data-term-url="/en/glossary/view/organism/2171">organisms</mark> their characteristics, this means that a cell entering prophase contains two copies of what is called the <em>genetic sequence</em>, or the <em>genome</em>, of an organism. What happens from this point forward is simply a matter of repackaging and relocating the chromatin.</p><p>Taking the five phases of <mark class="term" data-term="mitosis" data-term-def="Process occurring as part of the eukaryotic cell cycle. In mitosis, chromosomes in the cell nucleus separate into two identical chromosome&hellip;" data-term-url="/en/glossary/view/mitosis/10188">mitosis</mark> plus interphase, you can remember the entire <mark class="term" data-term="cell" data-term-def="The basic structural unit of all living things." data-term-url="/en/glossary/view/cell/8286">cell</mark> cycle with the phrase “<strong>P</strong>lease <strong>P</strong>our <strong>M</strong>e <strong>A</strong>nother <strong>T</strong>ea <strong>I</strong>nstead!” (Figure 3)</p> <div class="figure"> <figure> <button class="lightbox-button lightbox-button--icon" data-lightbox="" data-lightbox-src="/img/library/large_images/image_8220.jpg"> <img src="/img/library/modules/mid212/Image/VLObject-8220-150621040603.jpg" alt="Figure 3: An illustration of the phases of mitosis: interphase, prophase, prometaphase, metaphase, anaphase, and telophase. This process then leads to cytokinesis." /> </button> <figcaption> <p><strong>Figure 3</strong>: An illustration of the phases of mitosis: interphase, prophase, prometaphase, metaphase, anaphase, and telophase. This process then leads to cytokinesis.</p> <span class="credit">image ©NIGMS</span> </figcaption> </figure> </div> <p><strong>Prophase</strong> is the time when we can first see the <mark class="term" data-term="chromosome" data-term-def="The organized genetic structure of DNA with associated proteins that contains the hereditary information necessary for reproduction, protein manufacture, and other functions." data-term-url="/en/glossary/view/chromosome/3760">chromosomes</mark> under an <mark class="term" data-term="optical" data-term-def="Related to the science of light." data-term-url="/en/glossary/view/optical/8749">optical</mark> microscope. As noted above, the cell’s genetic sequence replicates prior to prophase (during interphase). During interphase, the <mark class="term" data-term="chromatin" data-term-def="Chromatin is the substance inside of the cell's nucleus and it consists of DNA, proteins (primarily histones), and chromosomal RNA. The&hellip;" data-term-url="/en/glossary/view/chromatin/9839">chromatin</mark> is relatively decondensed, bundled loosely, like spaghetti, and dispersed throughout the <mark class="term" data-term="nucleus" data-term-def="1. [Atomic] A tiny, dense positively charged mass at the heart of an atom. The nucleus is composed of protons and&hellip;" data-term-url="/en/glossary/view/nucleus/1526">nucleus</mark>. With the onset of prophase, the chromatin folds up into a compact form that, when stained with a dye, can be seen as individual chromosomes, even with the primitive microscopes available in Flemming’s era. Each chromosome consists of a pair of sister chromatids, each containing the same genetic sequence that was duplicated during interphase, and these two chromatids are connected by a structure called a <em>centromere</em>. Also, during prophase, a prominent structure called a <em>nucleolus</em> disappears from the nucleus.</p><p><strong>Prometaphase</strong> is marked by the breakdown of the <mark class="term" data-term="membrane" data-term-def="A thin layer of tissue that forms a boundary of a cell or cell part." data-term-url="/en/glossary/view/membrane/8282">membrane</mark> that surrounds the <mark class="term" data-term="cell" data-term-def="The basic structural unit of all living things." data-term-url="/en/glossary/view/cell/8286">cell</mark> <mark class="term" data-term="nucleus" data-term-def="1. [Atomic] A tiny, dense positively charged mass at the heart of an atom. The nucleus is composed of protons and&hellip;" data-term-url="/en/glossary/view/nucleus/1526">nucleus</mark>. Additionally, pairs of <mark class="term" data-term="protein" data-term-def="Macromolecules that are polymers of individual amino acids arranged in a chain and joined together by peptide bonds (and so also&hellip;" data-term-url="/en/glossary/view/protein/1594">protein</mark> complexes called <em>kinetochores</em> bind to the centromere of each <mark class="term" data-term="chromosome" data-term-def="The organized genetic structure of DNA with associated proteins that contains the hereditary information necessary for reproduction, protein manufacture, and other functions." data-term-url="/en/glossary/view/chromosome/3760">chromosome</mark>, one kinetochore for each chromatid. These two key events will allow for connections to form between the chromosomes and special structures located just outside of the nucleus.</p><p><strong>Metaphase</strong> is characterized by a repositioning of the duplicated <mark class="term" data-term="chromosome" data-term-def="The organized genetic structure of DNA with associated proteins that contains the hereditary information necessary for reproduction, protein manufacture, and other functions." data-term-url="/en/glossary/view/chromosome/3760">chromosomes</mark> so that they are ready to be pulled apart. During interphase, most animal <mark class="term" data-term="cell" data-term-def="The basic structural unit of all living things." data-term-url="/en/glossary/view/cell/8286">cells</mark> contain a structure called a <em>centrosome</em>, located near the <mark class="term" data-term="nucleus" data-term-def="1. [Atomic] A tiny, dense positively charged mass at the heart of an atom. The nucleus is composed of protons and&hellip;" data-term-url="/en/glossary/view/nucleus/1526">nucleus</mark> but outside of its <mark class="term" data-term="membrane" data-term-def="A thin layer of tissue that forms a boundary of a cell or cell part." data-term-url="/en/glossary/view/membrane/8282">membrane</mark>. Like the <mark class="term" data-term="chromatin" data-term-def="Chromatin is the substance inside of the cell's nucleus and it consists of DNA, proteins (primarily histones), and chromosomal RNA. The&hellip;" data-term-url="/en/glossary/view/chromatin/9839">chromatin</mark>, the centrosome also replicates toward the end of interphase, and by the onset of metaphase each of the two <mark class="term" data-term="daughter" data-term-def="A material that is derived from the breakdown or division of another. For example, a product of the radioactive decay of&hellip;" data-term-url="/en/glossary/view/daughter/10177">daughter</mark> centrosomes has migrated to opposite ends of the nuclear membrane. Throughout the cell cycle, the centrosome acts as the control center for <em>microtubules</em>, a complex <mark class="term" data-term="system" data-term-def="A group of interacting, interrelated or interdependent components that form a complex whole. The size of the system is defined for&hellip;" data-term-url="/en/glossary/view/system/3904">system</mark> of <mark class="term" data-term="protein" data-term-def="Macromolecules that are polymers of individual amino acids arranged in a chain and joined together by peptide bonds (and so also&hellip;" data-term-url="/en/glossary/view/protein/1594">protein</mark> fibers that make up the part of the cytoskeleton. Just as bones give shape to your body on a large scale, the cytoskeleton provides each cell with a shape, while also helping to transport materials. With the nuclear membrane now dissolved and the two centrosomes positioned on opposite sides of the cell, the condensed chromosomes line up along an imaginary line in the center of the cell called the <em>metaphase plate</em>. <mark class="term" data-term="microtubule" data-term-def="Microtubules are hollow cylinders of tubulin protein in the cytoplasm of all eukaryotic cells. As part of a cell's cytoskeleton, they&hellip;" data-term-url="/en/glossary/view/microtubule/9842">Microtubule</mark> fibers then begin to extend from each centrosome toward the centromere that connects the two sister chromatids of each chromosome. This cage-like structure of <mark class="term" data-term="microtubule" data-term-url="/en/glossary/view/microtubule" data-term-def="Microtubules are hollow cylinders of tubulin protein in the cytoplasm of all eukaryotic cells. As part of a cell's cytoskeleton, they&hellip;">microtubules</mark> is called the <em>mitotic spindle</em>. Specifically, the microtubule fibers attach to the kinetochores; as noted above, there are two <em>kinetochores</em>, one for each chromatid. This provides the setup for the chromatids to be pulled apart during the next phase.</p><p><strong>Anaphase</strong> is characterized by the separation of the two identical chromatids of each <mark class="term" data-term="chromosome" data-term-def="The organized genetic structure of DNA with associated proteins that contains the hereditary information necessary for reproduction, protein manufacture, and other functions." data-term-url="/en/glossary/view/chromosome/3760">chromosome</mark>. With the mitotic spindle complete, the two centrosomes start moving outward, pulling each chromatid away from its sister and toward opposite ends of the <mark class="term" data-term="cell" data-term-def="The basic structural unit of all living things." data-term-url="/en/glossary/view/cell/8286">cell</mark>.</p><p><strong>Telophase</strong> begins when the two sets of chromatids reach distinct regions of the <mark class="term" data-term="cell" data-term-def="The basic structural unit of all living things." data-term-url="/en/glossary/view/cell/8286">cell</mark> and a new nuclear <mark class="term" data-term="membrane" data-term-def="A thin layer of tissue that forms a boundary of a cell or cell part." data-term-url="/en/glossary/view/membrane/8282">membrane</mark> starts to form around each set. <mark class="term" data-term="cytokinesis" data-term-def="The process of cell division in the eukaryotic cell cycle, characterized by the cytoplasm dividing to form two daughter cells." data-term-url="/en/glossary/view/cytokinesis/10178">Cytokinesis</mark> also begins during telophase, even before the new nuclear membranes are complete. Once formed, however, each new nuclear membrane encloses a full set of <mark class="term" data-term="chromosome" data-term-def="The organized genetic structure of DNA with associated proteins that contains the hereditary information necessary for reproduction, protein manufacture, and other functions." data-term-url="/en/glossary/view/chromosome/3760">chromosomes</mark>. These then decondense into the ordinary <mark class="term" data-term="chromatin" data-term-def="Chromatin is the substance inside of the cell's nucleus and it consists of DNA, proteins (primarily histones), and chromosomal RNA. The&hellip;" data-term-url="/en/glossary/view/chromatin/9839">chromatin</mark> of interphase, a nucleolus appears in each newly formed <mark class="term" data-term="nucleus" data-term-def="1. [Atomic] A tiny, dense positively charged mass at the heart of an atom. The nucleus is composed of protons and&hellip;" data-term-url="/en/glossary/view/nucleus/1526">nucleus</mark>, and the cell cycle begins anew.</p><p><strong>Interphase</strong> is not a part of <mark class="term" data-term="mitosis" data-term-def="Process occurring as part of the eukaryotic cell cycle. In mitosis, chromosomes in the cell nucleus separate into two identical chromosome&hellip;" data-term-url="/en/glossary/view/mitosis/10188">mitosis</mark>, but is the <mark class="term" data-term="cell" data-term-def="The basic structural unit of all living things." data-term-url="/en/glossary/view/cell/8286">cell</mark>'s state between nuclear divisions when it is preparing for mitosis and <mark class="term" data-term="cytokinesis" data-term-def="The process of cell division in the eukaryotic cell cycle, characterized by the cytoplasm dividing to form two daughter cells." data-term-url="/en/glossary/view/cytokinesis/10178">cytokinesis</mark>. Interphase is discussed in more detail below.</p> <div class="comprehension-checkpoint margin-y-4"> <h6 class="comprehension-checkpoint__header"> <span> <span class="icon icon-question"></span> </span> Comprehension Checkpoint </h6> <form class="" name="cc7746"> <div class="form-entry"> <div class="form-entry__field"> <span class="form-entry__field__label">What name did Flemming give to the material that forms chromosomes?</span> <div class="form-entry__option"> <div class="form-entry__option__radio" data-answer="correct"> <label> <input id="q1-7746-0-option-a" name="quiz-option-7746" type="radio" value="chromatin" > <span class="option__label"> <span class="screen-reader-only">a.</span> chromatin </span> </label> <span class="quiz__response" id="response-7746-0"> <strong>Correct!</strong> </span> </div> <div class="form-entry__option__radio" data-answer="incorrect"> <label> <input id="q1-7746-1-option-b" name="quiz-option-7746" type="radio" value="prophase" > <span class="option__label"> <span class="screen-reader-only">b.</span> prophase </span> </label> <span class="quiz__response" id="response-7746-1"> <strong>Incorrect.</strong> </span> </div> </div> </div> </div> </form> </div> </section> <section id="toc_2"> <h2>Structure of cell components important to mitosis</h2></section> <section id="toc2_1"><h3>Structure of chromatin</h3><p>Chromatin consists of <mark class="term" data-term="DNA" data-term-def="Deoxyribonucleic acid. A double-stranded nucleic acid containing the sugar 2-deoxy-D-ribose. A constituent of cellular nuclear material responsible for encoding&hellip;" data-term-url="/en/glossary/view/DNA/1604">DNA</mark> and special <mark class="term" data-term="protein" data-term-def="Macromolecules that are polymers of individual amino acids arranged in a chain and joined together by peptide bonds (and so also&hellip;" data-term-url="/en/glossary/view/protein/1594">proteins</mark> called <em>histones</em>. DNA is a long <mark class="term" data-term="molecule" data-term-def="A particle formed by the chemical bonding of two or more atoms. The molecule is the smallest particle of a&hellip;" data-term-url="/en/glossary/view/molecule/1518">molecule</mark> consisting of two strands of repeating chemical <mark class="term" data-term="unit" data-term-def="An accepted quantity used as a standard of measurement. For example, the meter, liter, and gram." data-term-url="/en/glossary/view/unit/848">units</mark> called <mark class="term" data-term="nucleotide" data-term-def="The building blocks of DNA and RNA, consisting of a nitrogen base, a five-carbon sugar, and one or more phosphate groups." data-term-url="/en/glossary/view/nucleotide/1603">nucleotides</mark>. There are four types of nucleotides, and the genetic sequence is based on the order in which these four types of nucleotide are connected, one after the other, over the length of the molecule. It’s like a language built of words composed of only four possible letters, but it works well, because the DNA molecule allows each word to be very long (learn more in our series on DNA, specifically <a href="/library/module_viewer.php?mid=160">DNA II: The Structure of DNA</a>). The <mark class="term" data-term="density" data-term-def="A measure of the compactness of a substance given by the mass per unit volume (d = m/v). Common units of&hellip;" data-term-url="/en/glossary/view/density/863">density</mark> of <mark class="term" data-term="chromatin" data-term-def="Chromatin is the substance inside of the cell's nucleus and it consists of DNA, proteins (primarily histones), and chromosomal RNA. The&hellip;" data-term-url="/en/glossary/view/chromatin/9839">chromatin</mark> changes throughout the <mark class="term" data-term="cell" data-term-def="The basic structural unit of all living things." data-term-url="/en/glossary/view/cell/8286">cell</mark> cycle; this depends on how tightly the DNA strand is wrapped and tethered to histones and other associated proteins (Figure 4).</p> <div class="figure"> <figure> <button class="lightbox-button lightbox-button--icon" data-lightbox="" data-lightbox-src="/img/library/large_images/image_8221.jpg"> <img src="/img/library/modules/mid212/Image/VLObject-8221-150621040614.jpg" alt="Figure 4: The substance within chromosomes, chromatin, is made up of DNA (genetic information) and proteins (called histones)." /> </button> <figcaption> <p><strong>Figure 4</strong>: The substance within chromosomes, chromatin, is made up of DNA (genetic information) and proteins (called histones).</p> <span class="credit">image ©Darryl Leja, NHGRI & www.genome.gov</span> </figcaption> </figure> </div> <p>While <mark class="term" data-term="chromosome" data-term-def="The organized genetic structure of DNA with associated proteins that contains the hereditary information necessary for reproduction, protein manufacture, and other functions." data-term-url="/en/glossary/view/chromosome/3760">chromosomes</mark> are a way of organizing the <mark class="term" data-term="chromatin" data-term-def="Chromatin is the substance inside of the cell's nucleus and it consists of DNA, proteins (primarily histones), and chromosomal RNA. The&hellip;" data-term-url="/en/glossary/view/chromatin/9839">chromatin</mark> of <mark class="term" data-term="eukaryotic" data-term-def="Of cells with a nucleus and other organelles that are surrounded by lipid membranes" data-term-url="/en/glossary/view/eukaryotic/6539">eukaryotic</mark> <mark class="term" data-term="organism" data-term-def="Any connected living system, such as an animal, plant, fungus, or bacterium. Organisms may be composed of a single cell or&hellip;" data-term-url="/en/glossary/view/organism/2171">organisms</mark> into individual packages, the number of chromosomes varies widely among <mark class="term" data-term="eukaryote" data-term-def="A single- or multi-cellular organism whose cells contain a distinct nucleus that encloses the organism's genetic material." data-term-url="/en/glossary/view/eukaryote/5297">eukaryotes</mark>. Humans have 46, cats and other felines have 38, dogs have 78, and wheat has 42, while the Jack Jumper ant has only 2, and a certain kind of protozoan is famous for having nearly 16,000.</p><p>It should be emphasized that <mark class="term" data-term="mitosis" data-term-def="Process occurring as part of the eukaryotic cell cycle. In mitosis, chromosomes in the cell nucleus separate into two identical chromosome&hellip;" data-term-url="/en/glossary/view/mitosis/10188">mitosis</mark> occurs only in <mark class="term" data-term="eukaryotic" data-term-def="Of cells with a nucleus and other organelles that are surrounded by lipid membranes" data-term-url="/en/glossary/view/eukaryotic/6539">eukaryotic</mark> <mark class="term" data-term="cell" data-term-def="The basic structural unit of all living things." data-term-url="/en/glossary/view/cell/8286">cells</mark>, since only <mark class="term" data-term="eukaryote" data-term-def="A single- or multi-cellular organism whose cells contain a distinct nucleus that encloses the organism's genetic material." data-term-url="/en/glossary/view/eukaryote/5297">eukaryotes</mark> have membrane-bound nuclei. <mark class="term" data-term="bacteria" data-term-def="(plural of bacterium) A large group of one-celled organisms that are found almost everywhere." data-term-url="/en/glossary/view/bacteria/8679">Bacteria</mark> and <mark class="term" data-term="archaea" data-term-def="(plural of archaeon) One of three domains of life on Earth (the other two being <a href="http://www.visionlearning.com/en/glossary/index/B#term-8679">Bacteria</a> and <a href="http://www.visionlearning.com/en/glossary/index/E#term-5297">Eukaryota</a>), consisting&hellip;" data-term-url="/en/glossary/view/archaea/10172">Archaea</mark>, the other two domains of life, have <mark class="term" data-term="chromosome" data-term-def="The organized genetic structure of DNA with associated proteins that contains the hereditary information necessary for reproduction, protein manufacture, and other functions." data-term-url="/en/glossary/view/chromosome/3760">chromosomes</mark> that are not separated from the rest of the cell; consequently, they can reproduce through a simpler <mark class="term" data-term="process" data-term-def="Method, procedure; series of actions or steps." data-term-url="/en/glossary/view/process/8256">process</mark> called <mark class="term" data-term="binary fission" data-term-def="A form of asexual reproduction where a cell divides itself into two identical daughter cells." data-term-url="/en/glossary/view/binary+fission/6547">binary fission</mark> (to learn more, see our module <a href="/library/module_viewer.php?mid=64">The Discovery and Structure of Cells</a>).</p> <div class="comprehension-checkpoint margin-y-4"> <h6 class="comprehension-checkpoint__header"> <span> <span class="icon icon-question"></span> </span> Comprehension Checkpoint </h6> <form class="" name="cc7752"> <div class="form-entry"> <div class="form-entry__field"> <span class="form-entry__field__label">All living organisms have the same number of chromosomes.</span> <div class="form-entry__option"> <div class="form-entry__option__radio" data-answer="incorrect"> <label> <input id="q1-7752-0-option-a" name="quiz-option-7752" type="radio" value="true" > <span class="option__label"> <span class="screen-reader-only">a.</span> true </span> </label> <span class="quiz__response" id="response-7752-0"> <strong>Incorrect.</strong> </span> </div> <div class="form-entry__option__radio" data-answer="correct"> <label> <input id="q1-7752-1-option-b" name="quiz-option-7752" type="radio" value="false" > <span class="option__label"> <span class="screen-reader-only">b.</span> false </span> </label> <span class="quiz__response" id="response-7752-1"> <strong>Correct!</strong> </span> </div> </div> </div> </div> </form> </div> </section> <section id="toc2_2"><h3>Microtubules and centrosomes</h3><p>Just as <mark class="term" data-term="DNA" data-term-def="Deoxyribonucleic acid. A double-stranded nucleic acid containing the sugar 2-deoxy-D-ribose. A constituent of cellular nuclear material responsible for encoding&hellip;" data-term-url="/en/glossary/view/DNA/1604">DNA</mark> is a large <mark class="term" data-term="molecule" data-term-def="A particle formed by the chemical bonding of two or more atoms. The molecule is the smallest particle of a&hellip;" data-term-url="/en/glossary/view/molecule/1518">molecule</mark> constructed of building blocks, <mark class="term" data-term="microtubule" data-term-def="Microtubules are hollow cylinders of tubulin protein in the cytoplasm of all eukaryotic cells. As part of a cell's cytoskeleton, they&hellip;" data-term-url="/en/glossary/view/microtubule/9842">microtubules</mark> are made of repeating <mark class="term" data-term="unit" data-term-def="An accepted quantity used as a standard of measurement. For example, the meter, liter, and gram." data-term-url="/en/glossary/view/unit/848">units</mark> of <mark class="term" data-term="protein" data-term-def="Macromolecules that are polymers of individual amino acids arranged in a chain and joined together by peptide bonds (and so also&hellip;" data-term-url="/en/glossary/view/protein/1594">protein</mark> called <em>tubulin</em>. In addition to playing a structural role akin to the skeleton of your body, large molecules built of tubulin subunits are vital to <mark class="term" data-term="mitosis" data-term-def="Process occurring as part of the eukaryotic cell cycle. In mitosis, chromosomes in the cell nucleus separate into two identical chromosome&hellip;" data-term-url="/en/glossary/view/mitosis/10188">mitosis</mark> and several other dynamic <mark class="term" data-term="cell" data-term-def="The basic structural unit of all living things." data-term-url="/en/glossary/view/cell/8286">cell</mark> functions. They actually move, which is why <mark class="term" data-term="chromosome" data-term-def="The organized genetic structure of DNA with associated proteins that contains the hereditary information necessary for reproduction, protein manufacture, and other functions." data-term-url="/en/glossary/view/chromosome/3760">chromosomes</mark> can be pulled apart, and why the entire cell can be made to divide.</p><p>All of this takes a great deal of organization, and so <mark class="term" data-term="eukaryotic" data-term-def="Of cells with a nucleus and other organelles that are surrounded by lipid membranes" data-term-url="/en/glossary/view/eukaryotic/6539">eukaryotic</mark> <mark class="term" data-term="cell" data-term-def="The basic structural unit of all living things." data-term-url="/en/glossary/view/cell/8286">cells</mark> depend on components known as <em>microtubule organizing centers</em> (MTOCs). In animal cells, the centrosome is one of the main types of MTOC. As we shall see in the next section, two centrosomes are needed during <mark class="term" data-term="mitosis" data-term-def="Process occurring as part of the eukaryotic cell cycle. In mitosis, chromosomes in the cell nucleus separate into two identical chromosome&hellip;" data-term-url="/en/glossary/view/mitosis/10188">mitosis</mark> of an animal cell, each member of the pair using <mark class="term" data-term="microtubule" data-term-def="Microtubules are hollow cylinders of tubulin protein in the cytoplasm of all eukaryotic cells. As part of a cell's cytoskeleton, they&hellip;" data-term-url="/en/glossary/view/microtubule/9842">microtubules</mark> to pull a set of <mark class="term" data-term="daughter" data-term-def="A material that is derived from the breakdown or division of another. For example, a product of the radioactive decay of&hellip;" data-term-url="/en/glossary/view/daughter/10177">daughter</mark> <mark class="term" data-term="chromosome" data-term-def="The organized genetic structure of DNA with associated proteins that contains the hereditary information necessary for reproduction, protein manufacture, and other functions." data-term-url="/en/glossary/view/chromosome/3760">chromosomes</mark> toward one end of the dividing cell. A centrosome consists of two <mark class="term" data-term="centrioles" data-term-def="Eukaryotic cells depend on organelles known as centrioles to help organize microtubules during cell reproduction (mitosis and meiosis). The centrioles are&hellip;" data-term-url="/en/glossary/view/centrioles/9840">centrioles</mark> that are made of tubulin. The two centrioles are arranged at right angles, or orthogonally, and are surrounded by other <mark class="term" data-term="protein" data-term-def="Macromolecules that are polymers of individual amino acids arranged in a chain and joined together by peptide bonds (and so also&hellip;" data-term-url="/en/glossary/view/protein/1594">proteins</mark> that make the centrosome more than just a bent section of microtubule (Figure 5).</p> <div class="figure"> <figure> <button class="lightbox-button lightbox-button--icon" data-lightbox="" data-lightbox-src="/img/library/large_images/image_8222.jpg"> <img src="/img/library/modules/mid212/Image/VLObject-8222-150621040642.jpg" alt="Figure 5: Illustration of a centrosome, which consists of two barrel-like centrioles (each made of tubulin) at right angles to each other." /> </button> <figcaption> <p><strong>Figure 5</strong>: Illustration of a centrosome, which consists of two barrel-like centrioles (each made of tubulin) at right angles to each other.</p> <span class="credit">image ©Darryl Leja, NHGRI & www.genome.gov</span> </figcaption> </figure> </div> </section> <section id="toc_3"> <h2>Interphase: normal life functions and preparation for mitosis</h2><p>Although not part of <mark class="term" data-term="mitosis" data-term-def="Process occurring as part of the eukaryotic cell cycle. In mitosis, chromosomes in the cell nucleus separate into two identical chromosome&hellip;" data-term-url="/en/glossary/view/mitosis/10188">mitosis</mark>, interphase is important to discuss because it places mitosis into context with respect to the <mark class="term" data-term="cell" data-term-def="The basic structural unit of all living things." data-term-url="/en/glossary/view/cell/8286">cell</mark> cycle. For <mark class="term" data-term="vertebrate" data-term-def="Any organism with a backbone. Only ~5% of described animal species are vertebrates." data-term-url="/en/glossary/view/vertebrate/5332">vertebrates</mark> (the subphylum of animals to which humans belong), the duration of the life cycle of each cell varies, depending on the cell type. Certain white blood cells may live and be replaced over a period lasting less than a day. Most other body cell types have life cycles ranging from days to months. Others, such as bone cells, typically are replaced in cycles measured in decades, while certain brain cells and muscle cells will endure for the entire lifespan of the <mark class="term" data-term="organism" data-term-def="Any connected living system, such as an animal, plant, fungus, or bacterium. Organisms may be composed of a single cell or&hellip;" data-term-url="/en/glossary/view/organism/2171">organism</mark>. These cells are said to be in a permanent interphase; specifically, they are locked in a phase of interphase known as <em>G1</em>.</p><p>For <mark class="term" data-term="cell" data-term-def="The basic structural unit of all living things." data-term-url="/en/glossary/view/cell/8286">cells</mark> that will be moving from interphase into a new round of <mark class="term" data-term="mitosis" data-term-def="Process occurring as part of the eukaryotic cell cycle. In mitosis, chromosomes in the cell nucleus separate into two identical chromosome&hellip;" data-term-url="/en/glossary/view/mitosis/10188">mitosis</mark>, the G1 phase ends at what’s called the restriction point, when the cell commits to replication, and enters the phase of <mark class="term" data-term="DNA" data-term-def="Deoxyribonucleic acid. A double-stranded nucleic acid containing the sugar 2-deoxy-D-ribose. A constituent of cellular nuclear material responsible for encoding&hellip;" data-term-url="/en/glossary/view/DNA/1604">DNA</mark> <mark class="term" data-term="synthesis" data-term-def="The production of a chemical compound by combining simpler compounds or elements." data-term-url="/en/glossary/view/synthesis/8756">synthesis</mark>, or <em>S phase</em>. Throughout G1, sections of the decondensed <mark class="term" data-term="chromosome" data-term-def="The organized genetic structure of DNA with associated proteins that contains the hereditary information necessary for reproduction, protein manufacture, and other functions." data-term-url="/en/glossary/view/chromosome/3760">chromosomes</mark> are accessed as needed by <mark class="term" data-term="enzyme" data-term-def="Molecules produced by living organisms that help catalyze biochemical reactions. Enzymes are predominantly protein or protein-based molecules and are highly&hellip;" data-term-url="/en/glossary/view/enzyme/1595">enzymes</mark> using the DNA sequence to make <mark class="term" data-term="protein" data-term-def="Macromolecules that are polymers of individual amino acids arranged in a chain and joined together by peptide bonds (and so also&hellip;" data-term-url="/en/glossary/view/protein/1594">proteins</mark>, but in the S phase the entire collection of genetic material is copied. Thus, by the end of the S phase, each decondensed chromosome exists in duplicate, the two copies destined to become the two sister chromatids when the chromosome condenses at prophase. Generally the S phase leads into a transitional phase known as <em>G2</em>, although the cells of some animal <mark class="term" data-term="species" data-term-def="1. In biological classifications, it is the lowest and most basic unit of the Linnaean taxonomic hierarchy (although it is also&hellip;" data-term-url="/en/glossary/view/species/893">species</mark> proceed from the S phase directly into mitosis. During G2, proteins are synthesized that will support mitosis and <mark class="term" data-term="cytokinesis" data-term-def="The process of cell division in the eukaryotic cell cycle, characterized by the cytoplasm dividing to form two daughter cells." data-term-url="/en/glossary/view/cytokinesis/10178">cytokinesis</mark>. Additionally, many cell types undergo a kind of self-testing to make sure that everything is correct before mitosis begins, and certain cancers are thought to result from cells missing the G2 phase and thus avoiding the testing that would prevent mitosis in cases when all is not right. (You can learn about interphase in detail in our <a href="/library/module_viewer.php?mid=196">Cell Division I: The Cell Cycle</a> module.) A representation of cell cycle phases is shown in Figure 6.</p> <div class="figure"> <figure> <button class="lightbox-button lightbox-button--icon" data-lightbox="" data-lightbox-src="/img/library/large_images/image_6592.jpg"> <img src="/img/library/modules/mid212/Image/VLObject-6592-131031121042.jpg" alt="Figure 6: Relative lengths of the cell cycle phases, including the G1, S, and G2 phases that make up interphase. Mitosis, here noted by M, is a relatively short period." /> </button> <figcaption> <p><strong>Figure 6:</strong> Relative lengths of the cell cycle phases, including the G<sub>1</sub>, S, and G<sub>2</sub> phases that make up interphase. Mitosis, here noted by M, is a relatively short period.</p> </figcaption> </figure> </div> <div class="comprehension-checkpoint margin-y-4"> <h6 class="comprehension-checkpoint__header"> <span> <span class="icon icon-question"></span> </span> Comprehension Checkpoint </h6> <form class="" name="cc7759"> <div class="form-entry"> <div class="form-entry__field"> <span class="form-entry__field__label">____________ remain in a permanent interphase.</span> <div class="form-entry__option"> <div class="form-entry__option__radio" data-answer="correct"> <label> <input id="q1-7759-0-option-a" name="quiz-option-7759" type="radio" value="Brain cells" > <span class="option__label"> <span class="screen-reader-only">a.</span> Brain cells </span> </label> <span class="quiz__response" id="response-7759-0"> <strong>Correct!</strong> </span> </div> <div class="form-entry__option__radio" data-answer="incorrect"> <label> <input id="q1-7759-1-option-b" name="quiz-option-7759" type="radio" value="White blood cells" > <span class="option__label"> <span class="screen-reader-only">b.</span> White blood cells </span> </label> <span class="quiz__response" id="response-7759-1"> <strong>Incorrect.</strong> </span> </div> </div> </div> </div> </form> </div> </section> <section id="toc_4"> <h2>Questions and answers from the periwinkle plant</h2><p>Painstaking, systematic work like Flemming’s is one way to make a discovery. Indeed, in modern science, it’s the most common way. But it’s not the only way. One major discovery very relevant to <mark class="term" data-term="mitosis" data-term-def="Process occurring as part of the eukaryotic cell cycle. In mitosis, chromosomes in the cell nucleus separate into two identical chromosome&hellip;" data-term-url="/en/glossary/view/mitosis/10188">mitosis</mark> came unexpectedly, and from a surprising source: tea leaves. Not conventional tea, but leaves of the Madagascar Periwinkle, a plant known for its beautiful flowers. </p></section> <section id="toc2_3"><h3><em>Vinca rosea</em> and diabetes</h3><p>In many parts of the world, people brew tea from leaves of the Periwinkle (Figure 7), previously called <em>Vinca rosea</em> and now designated as <em>Catharanthus roseus</em> (we'll use the older <em>Vinca</em> name here). This tea is used as a folk remedy for a plethora of ailments, but especially for diabetes when insulin and other conventional treatments are not available. It’s an ancient remedy whose potential in diabetes treatment science has only recently begun to uncover, but it first met the scrutiny of modern <mark class="term" data-term="research" data-term-def="A study or an investigation." data-term-url="/en/glossary/view/research/8257">research</mark> back in the 1950s. Fascinated to hear of the tradition, a Canadian endocrinologist from Toronto, Clark Noble, accepted a sample of 25 Periwinkle leaves from a patient who had acquired them in Jamaica. Although recently retired from endocrinology research, Noble had been a key player in the discovery of insulin 30 years earlier, but the <mark class="term" data-term="Nobel Prize" data-term-def="Awards made annually, beginning in 1901, from funds originally established by Alfred B. Nobel for outstanding achievement in physics, chemistry, medicine&hellip;" data-term-url="/en/glossary/view/Nobel+Prize/3843">Nobel Prize</mark> for this milestone medical advance had eluded him. Others who had worked closely with Noble had received the award, but he was remembered as merely a sideline figure. If diabetics in Jamaica and elsewhere really were benefiting from the <em>Vinca</em> plant, Noble wanted to know how it worked. Lacking a lab of his own, he sent the envelope to the lab of his younger brother, Robert.</p> <div class="figure"> <figure> <button class="lightbox-button lightbox-button--icon" data-lightbox="" data-lightbox-src="/img/library/large_images/image_8223.jpg"> <img src="/img/library/modules/mid212/Image/VLObject-8223-150621050650.jpg" alt="Figure 7: The Madagascar Periwinkle plant (Catharanthus roseus, previously called Vinca rosea)." /> </button> <figcaption> <p><strong>Figure 7</strong>: The Madagascar Periwinkle plant (<em>Catharanthus roseus</em>, previously called <em>Vinca rosea</em>).</p> </figcaption> </figure> </div> <p>Also an endocrinology researcher, Robert Noble jumped at the opportunity to study the leaves. As noted above, insulin treatment had been available for only 30 years at this point. It was obtained from pigs, and supplies were not particularly abundant. Moreover, it didn’t work well for all diabetic patients. Today we know this has to do with the fact that there are two main types of diabetes, both of which manifest as an inability to <mark class="term" data-term="absorb" data-term-def="Take in or soak up (energy, liquids, or other substances), usually gradually, through a chemical or physical action." data-term-url="/en/glossary/view/absorb/11219">absorb</mark> <mark class="term" data-term="sugar" data-term-def="A water-soluble crystalline carbohydrate. There are many types of sugar of varying degrees of sweetness, including fructose, which occurs naturally in&hellip;" data-term-url="/en/glossary/view/sugar/5309">sugar</mark> from the blood into the body’s muscle <mark class="term" data-term="cell" data-term-def="The basic structural unit of all living things." data-term-url="/en/glossary/view/cell/8286">cells</mark>, leading to a range of long-term complications in many body <mark class="term" data-term="system" data-term-def="A group of interacting, interrelated or interdependent components that form a complex whole. The size of the system is defined for&hellip;" data-term-url="/en/glossary/view/system/3904">systems</mark>. Some diabetics are unable to produce insulin, so taking insulin works very well for them. In others, however, the problem is that their muscle cells do not respond well to insulin. They produce insulin, and yet their blood sugar levels are still high. Insulin may help them a little, but not completely, and for some it does not help at all. Today, we have drugs to make their muscle cells more sensitive to insulin, but the situation was very different back in the 1950s. And thus, Robert Noble happily set out to study the <em>Vinca</em> leaves that his older brother had sent him.</p><p>Noble started by formulating questions that could be answered through <mark class="term" data-term="experiment" data-term-def="A test or trial carried out under controlled conditions so that specific actions can be performed and the results can be observed." data-term-url="/en/glossary/view/experiment/8292">experiments</mark> on laboratory animals such as rabbits and mice. When injected, would an extract of the leaves lower an animal’s blood sugar? Would it prevent the development of diabetic symptoms like excessive urination? Would it prevent the development of blood <mark class="term" data-term="circulation" data-term-def="Generally, movement within a system. 1. [Atmospheric] the movement of air masses within the troposphere, driven by the redistribution of energy&hellip;" data-term-url="/en/glossary/view/circulation/10355">circulation</mark> problems and blindness? Or, injected into an animal that already has full-blown diabetes, would it reverse the condition? Using laboratory animals that have a certain medical condition in order to test an agent that might affect that condition is known as an <em>animal model</em>. In this case, Noble was employing rabbit and mice <mark class="term" data-term="model" data-term-def="A representation, pattern, or mathematical description that can help scientists replicate a system." data-term-url="/en/glossary/view/model/8236">models</mark> of diabetes.</p><p>After running a series of <mark class="term" data-term="experiment" data-term-def="A test or trial carried out under controlled conditions so that specific actions can be performed and the results can be observed." data-term-url="/en/glossary/view/experiment/8292">experiments</mark>, the younger Noble found that the <em>Vinca rosea</em> extract actually had no effect on diabetes whatsoever. In fact, at very high doses, it made the animals <em>really</em> sick. They were dying of infections, because their white blood <mark class="term" data-term="cell" data-term-def="The basic structural unit of all living things." data-term-url="/en/glossary/view/cell/8286">cell</mark> counts were too low. Something from the <em>Vinca</em> leaves was preventing the bone marrow from producing new white blood cells, which form the basis of the immune <mark class="term" data-term="system" data-term-def="A group of interacting, interrelated or interdependent components that form a complex whole. The size of the system is defined for&hellip;" data-term-url="/en/glossary/view/system/3904">system</mark>.</p></section> <section id="toc2_4"><h3><em>Vinca rosea</em> and white blood cells</h3><p>Noble didn’t know why the <em>Vinca</em> extract killed the white blood <mark class="term" data-term="cell" data-term-def="The basic structural unit of all living things." data-term-url="/en/glossary/view/cell/8286">cells</mark> of mice, but he wondered if this <mark class="term" data-term="property" data-term-def="A characteristic or attribute." data-term-url="/en/glossary/view/property/8555">property</mark> could be useful for people who have <em>too many</em> white blood cells. In other words, he wondered if the <em>Vinca</em> extract could be used to treat leukemia, a type of cancer characterized by excessively high numbers of white blood cells? To find out, Noble joined forces with chemist C.T. Beer to isolate the specific chemical <mark class="term" data-term="compound" data-term-def="A material formed by the chemical combination of elements in defined proportions. Compounds can be chemically decomposed into simpler substances." data-term-url="/en/glossary/view/compound/1517">compound</mark> from the <em>Vinca</em> extract that caused the effect.</p><p>They found the <mark class="term" data-term="compound" data-term-def="A material formed by the chemical combination of elements in defined proportions. Compounds can be chemically decomposed into simpler substances." data-term-url="/en/glossary/view/compound/1517">compound</mark> that belongs to a class of chemicals known as <mark class="term" data-term="alkaloid" data-term-def="Any of a class of nitrogen-containing organic compounds that come from plants and have an effect on the body. Common alkaloids&hellip;" data-term-url="/en/glossary/view/alkaloid/8754">alkaloids</mark>, and they named it vinblastine. Switching from an animal <mark class="term" data-term="model" data-term-def="A representation, pattern, or mathematical description that can help scientists replicate a system." data-term-url="/en/glossary/view/model/8236">model</mark> of diabetes to one of leukemia, Robert Noble began a new series of <mark class="term" data-term="experiment" data-term-def="A test or trial carried out under controlled conditions so that specific actions can be performed and the results can be observed." data-term-url="/en/glossary/view/experiment/8292">experiments</mark> looking at the effects of vinblastine on leukemia and some other diseases that are caused by uncontrolled replication of <mark class="term" data-term="cell" data-term-def="The basic structural unit of all living things." data-term-url="/en/glossary/view/cell/8286">cells</mark>. </p><p>Following success with the animal <mark class="term" data-term="experiment" data-term-def="A test or trial carried out under controlled conditions so that specific actions can be performed and the results can be observed." data-term-url="/en/glossary/view/experiment/8292">experiments</mark>, vinblastine proved to be very effective in clinical trials of cancer patients in Toronto. Soon, a related <mark class="term" data-term="compound" data-term-def="A material formed by the chemical combination of elements in defined proportions. Compounds can be chemically decomposed into simpler substances." data-term-url="/en/glossary/view/compound/1517">compound</mark> called vincristine was isolated by another investigator. A whole range of additional <em>Vinca</em> compounds followed, and each proved useful against various types of cancer, though vinblastine and vincristine are the most famous.</p><p>How well did they work? To give you an idea, <em>Vinca</em> drugs are still used today, often in combinations with other chemotherapy drugs, and they have led to dramatic increases in cancer survival. Vincristine, for instance, is part of the combination cocktail against the most common childhood leukemia known as acute lymphoblastic leukemia (ALL). In 1950, an ALL diagnosis was a virtual death sentence for a child, with a survival rate of 5 percent. Today, the survival rate of ALL is up to 95 percent. Similarly, Hodgkin disease – a type of cancer of the lymph nodes that often affects young adults – had a pitiful survival rate in the 1950s, but by 1980 the death rate from Hodgkin disease had decreased by 75 percent, thanks in large part to vinblastine, the drug that Noble discovered in the <em>Vinca</em> leaves.</p><p>All of this came from two brothers who had not even set out to do cancer <mark class="term" data-term="research" data-term-def="A study or an investigation." data-term-url="/en/glossary/view/research/8257">research</mark>. Unlike Walther Flemming, who had a plan and knew precisely what he was looking for, the discovery of vinblastine is a story of serendipity, or a fortunate accident.</p> <div class="comprehension-checkpoint margin-y-4"> <h6 class="comprehension-checkpoint__header"> <span> <span class="icon icon-question"></span> </span> Comprehension Checkpoint </h6> <form class="" name="cc7773"> <div class="form-entry"> <div class="form-entry__field"> <span class="form-entry__field__label">The <em>Vinca</em> extract was effective in treating</span> <div class="form-entry__option"> <div class="form-entry__option__radio" data-answer="incorrect"> <label> <input id="q1-7773-0-option-a" name="quiz-option-7773" type="radio" value="diabetes." > <span class="option__label"> <span class="screen-reader-only">a.</span> diabetes. </span> </label> <span class="quiz__response" id="response-7773-0"> <strong>Incorrect.</strong> </span> </div> <div class="form-entry__option__radio" data-answer="correct"> <label> <input id="q1-7773-1-option-b" name="quiz-option-7773" type="radio" value="diseases caused by cells replicating too fast." > <span class="option__label"> <span class="screen-reader-only">b.</span> diseases caused by cells replicating too fast. </span> </label> <span class="quiz__response" id="response-7773-1"> <strong>Correct!</strong> </span> </div> </div> </div> </div> </form> </div> </section> <section id="toc2_5"><h3>Cancer and mitosis</h3><p>How could a chemical drawn from a plant be so effective against leukemia? What does vinblastine do to the <mark class="term" data-term="cell" data-term-def="The basic structural unit of all living things." data-term-url="/en/glossary/view/cell/8286">cells</mark> of rabbits, mice, and people with cancer? Today, when pathologists look at suspected cancer under a microscope, they pay a lot of attention to <mark class="term" data-term="mitosis" data-term-def="Process occurring as part of the eukaryotic cell cycle. In mitosis, chromosomes in the cell nucleus separate into two identical chromosome&hellip;" data-term-url="/en/glossary/view/mitosis/10188">mitosis</mark>. Each time mitosis occurs, it leads to the <mark class="term" data-term="parent" data-term-def="The material or source from which something is derived." data-term-url="/en/glossary/view/parent/1618">parent</mark> cell splitting into two new <mark class="term" data-term="daughter" data-term-def="A material that is derived from the breakdown or division of another. For example, a product of the radioactive decay of&hellip;" data-term-url="/en/glossary/view/daughter/10177">daughter</mark> cells. While that <mark class="term" data-term="formula" data-term-def="An expression of the composition of a chemical compound using symbols." data-term-url="/en/glossary/view/formula/8554">formula</mark> is always the same, the rate at which mitosis occurs varies substantially. Just like other cells in a body, the life cycle of different cancer cells can vary. Some have a very short life cycle, with mitosis occurring frequently, while in other cancer cells mitosis is infrequent. When cancer is suspected, the pathologist looks at how fast and how often mitosis occurs. Cancer cells that undergo more mitosis tend to be more aggressive than cancer cells in which mitosis is more relaxed. This means that if you slow down mitosis, you might then be able to slow down, or even reverse, the progression of cancer.</p><p>It turns out that this is exactly how the <em>Vinca</em> <mark class="term" data-term="alkaloid" data-term-def="Any of a class of nitrogen-containing organic compounds that come from plants and have an effect on the body. Common alkaloids&hellip;" data-term-url="/en/glossary/view/alkaloid/8754">alkaloids</mark> work. When Robert Noble gave the Periwinkle tea to laboratory animals, and later when he gave the isolated vinblastine <mark class="term" data-term="compound" data-term-def="A material formed by the chemical combination of elements in defined proportions. Compounds can be chemically decomposed into simpler substances." data-term-url="/en/glossary/view/compound/1517">compound</mark> to human patients, <mark class="term" data-term="cell" data-term-def="The basic structural unit of all living things." data-term-url="/en/glossary/view/cell/8286">cell</mark> division slowed down in the white blood cells. It was later discovered that the compound interferes with <mark class="term" data-term="mitosis" data-term-def="Process occurring as part of the eukaryotic cell cycle. In mitosis, chromosomes in the cell nucleus separate into two identical chromosome&hellip;" data-term-url="/en/glossary/view/mitosis/10188">mitosis</mark>. In addition, the various <em>Vinca</em> compounds that were eventually discovered each interfere with mitosis at different phases and for different reasons. It turns out that the compounds disrupt the assembly of <mark class="term" data-term="microtubule" data-term-def="Microtubules are hollow cylinders of tubulin protein in the cytoplasm of all eukaryotic cells. As part of a cell's cytoskeleton, they&hellip;" data-term-url="/en/glossary/view/microtubule/9842">microtubules</mark> – the special fibers that provide structure in the cell. Vinblastine binds to the tubulin subunits, preventing them from coming together.</p><p>The questions that Robert Noble and the <mark class="term" data-term="generation" data-term-def="Offspring at the same step in the line of descent from a common ancestor." data-term-url="/en/glossary/view/generation/8293">generations</mark> of cancer researchers who stood on his shoulders were inspired to ask ultimately were investigated in a very systematic way. Having an idea of what they were looking for, researchers isolated new drugs and honed in more closely on the workings of the <mark class="term" data-term="microtubule" data-term-def="Microtubules are hollow cylinders of tubulin protein in the cytoplasm of all eukaryotic cells. As part of a cell's cytoskeleton, they&hellip;" data-term-url="/en/glossary/view/microtubule/9842">microtubule</mark> system. So while it may start with a lucky find, ultimately scientific advancement requires a clear plan, and long lasting, painstaking work.</p> </div> </section> <hr class="border-color-dark" /> <footer class="module__footer"> <p class="citation"> <em> David Warmflash, MD, Nathan H Lents, Ph.D. “Cell Division II” Visionlearning Vol. BIO-4 (2), 2015. </em> </p>  <div class="title-list" name="further"> <p class="h6 title-list__title"> Further Reading </p> <ul class="grid grid--column-2--md grid--column-3--md gap-1"> <li> <a class="no-hover-focus height-100" href="/en/library/Biology/2/Cellular-Organelles-I/195"> <article class="flex-row align-items-center flex-column--md align-items-start--md height-100 theme-light padding-2 gap-2"> <div class="width-30 width-auto--md"> <img class="border-radius box-shadow-1" src="/img/library/moduleImages/featured_image_195-23061209062726.jpeg" alt="Cellular Organelles I"> </div> <div class="flex-grow-shrink"> <h2 class="h6 font-weight-normal"> Cellular Organelles I: <em>Endosymbiosis and membrane-bound organelles</em> </h2> </div> </article> </a> </li> </ul> </div> </footer> </div>   </div>  <div class="order-1 order-2--lg module__tools"> <div class="narrow margin-x-auto position-sticky-top font-size-md"> <div class="padding-2 border-radius box-shadow-1--lg"> <div class="tabs" role="tablist"> <nav> <button class="button button--icon-label" id="tab-button-in-this-module" aria-label="Table of Contents" aria-controls="tab-panel-module__tools" aria-selected="true" role="tab"> <span class="icon icon-list" aria-hidden="true"></span> <span class="button__text">Contents</span> </button> <button class="button button--icon-label" id="tab-button-toggle-terms" aria-controls="tab-panel-toggle-terms" aria-selected="false" role="tab"> <span class="icon icon-glossary-highlight"></span> <span class="button__text">Glossary Terms</span> </button> </nav> <hr class="divider" /> <div class="tabs__panel shown" id="tab-panel-module__tools" aria-labelledby="tab-button-module__tools" role="tabpanel"> <p class="font-weight-bold margin-bottom-1"> Table of Contents </p> <div class="table-of-contents" id="module-toc"> <ul> <li><a href="/en/library/biology/2/cell-division-ii/212#toc_1">The phases of mitosis</a> </li> <li><a href="/en/library/biology/2/cell-division-ii/212#toc_2">Structure of cell components important to mitosis</a> </li> <li> <ul> <li><a href="/en/library/biology/2/cell-division-ii/212#toc2_1">Structure of chromatin</a> </li> </ul> </li> <li> <ul> <li><a href="/en/library/biology/2/cell-division-ii/212#toc2_2">Microtubules and centrosomes</a> </li> </ul> </li> <li><a href="/en/library/biology/2/cell-division-ii/212#toc_3">Interphase: normal life functions and preparation for mitosis</a> </li> <li><a href="/en/library/biology/2/cell-division-ii/212#toc_4">Questions and answers from the periwinkle plant</a> </li> <li> <ul> <li><a href="/en/library/biology/2/cell-division-ii/212#toc2_3">Vinca rosea and diabetes</a> </li> </ul> </li> <li> <ul> <li><a href="/en/library/biology/2/cell-division-ii/212#toc2_4">Vinca rosea and white blood cells</a> </li> </ul> </li> <li> <ul> <li><a href="/en/library/biology/2/cell-division-ii/212#toc2_5">Cancer and mitosis</a> </li> </ul> </li> </ul> </div> </div>   <div class="tabs__panel" id="tab-panel-toggle-terms" aria-labelledby="tab-button-toggle-terms" role="tabpanel"> <div class="reading-toggle"> <div class="reading-toggle__switch"> <div class="form-entry__option__switch"> <label> <input type="checkbox" name="termsToggleSwitch" id="terms-toggle-switch" /> <span class="switch__slider"></span> <span class="option__label text-decoration-none font-size-md"> Highlight Glossary Terms </span> </label> </div> </div> <div class="reading-toggle__help"> <p> <em> Activate glossary term highlighting to easily identify key terms within the module. 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